LASIK (Laser-Assisted In Situ Keratomileusis) is a surgical procedure intended to reduce a person's dependency on glasses or contact lenses. LASIK permanently changes the shape of the cornea, the clear covering of the front of the eye, using an excimer laser. A device, called a microkeratome, is used to cut a flap in the cornea. A hinge is left at one end of this flap. The flap is folded back revealing the stroma, the middlesection of the cornea. Pulses from a computer-controlled laser vaporize a portion of the stroma and the flap is replaced. It is important that the knife used during the LASIK procedure is sharp, otherwise the quality of the procedure and the healing time are poor. Additionally the knife has to be sharp in order to produce consistent and reproducible flaps. There are some complications related to the use of microkeratomes. The most common complication is the creation of an irregular flap, for example, a half flap, buttonhole, or total cup. These complications represent irregular incisions of the cornea, a situation that can permanently degrade visual performance.
Before LASIK, PRK (Photo-Refractive Keratectomy) was used to correct the curvature of the cornea. A physician could scrape away a superficial layer, e.g., the epithelium, of the cornea. After the superficial layer was removed, laser treatment was applied on to the exposed surface of the cornea. A problem existed, however, in that the healing period for the eye typically lasted for a week, much longer than the healing period of LASIK. Also, the patient experienced a lot of pain during healing. Typically in PRK a disposable contact lens is used to cover the treated area of the cornea and help reduce postoperative pain.
In another technique, LASEK (Laser Epithelial Keratomileusis) the epithelial layer is separated from the surface of the cornea in a manner that the separated epithelial layer can be preserved. First, the epithelium is treated with and alcohol solution to partially devitalize it. Once the exact surface area of treatment is determined, a few drops of a weak alcohol solution is applied to the surface of the cornea and allowed to stay in contact with the epithelium for a few seconds. This weak alcohol solution is then rinsed off the surface of the eye. The function of the weak alcohol solution is to loosen the epithelial layer (50 microns) and to allow it to be peeled back in a sheet of epithelial cells, thereby exposing the underlying cornea. This is not to be confused with LASIK, which actually uses a microkeratome instrument to create a flap of both epithelium and the front part of the stromal tissue measuring anywhere between 130 to 180 microns.
In LASEK, the epithelium-only layer is laid back in a similar fashion to LASIK, but consists of only epithelium, not corneal stroma. Once the epithelial cells have been laid out of the way, the laser is applied to the surface of the cornea in the exact same fashion as in PRK. Once the laser treatment has been completed, the epithelial layer is laid back into place and a soft contact lens is placed over the eye as in PRK. The epithelial cells, which were partly devitalized by the weak alcohol solution, are laid over the treatment area and may serve as a facilitator of new epithelium healing underneath. The alcohol-devitalized epithelium falls off the eye, similar to a scab, in 5-10 days. These devitalized epithelial cells do not become the new surface of the eye, but simply serve as a protective agent in addition to the contact lens to facilitate comfort and healing of the new underlying epithelium. Alcohol treatment of the epithelium results in a severe amount of epithelial cell loss, a fact that may render the epithelial disk not usable, due to the reduced durability and adhesion on to the cornea.
Thus, there is a need for an automated corneal epithelium separator that addresses the above problems by separating the epithelial layer as a whole in a mechanical way, not chemical.